Sulfur binder test

Microchemical testing is not only based on dissolution of binders but also on pigment and binder color reactions with oxidizing, dehydrating, or reducing agents. These tests are destructive diphenyla-mine (in concentrated sulfuric acid and glacial acetic acid) and LeRosen (formaldehyde in concentrated sulfuric acid) tests are typically used. 

In sodium hydroxide and hot sulfuric acid tests, K801 has shown better corrosion resistance than K701. K801 can also be used to advantage in radioactive atmospheres because the nickel binder has a much shorter half-life than the cobalt used as a binding element in most other carbides. 

This is especially true in industrial and urban areas. Fig. 87 shows a paint containing Chrome Yellow, which was subjected to a test as described in Section 1.6.2.2 treatment with 1 N sulfuric acid for one hour at 70°C. The distinct color change on the circular test area is accompanied by a considerable gloss reduction. In the corresponding lead chromate-free system, it is only the binder that is affected, which reduces the gloss the color value on the other hand is retained. 

The optimum or minimum allowable substitution ratio is then established by means of a series of justification tests at different binder contents. Figure 15 shows a comparison between the Marshall design properties of a conventional mixture using an asphalt binder and a 30 70 SEA binder. As indicated the optimum substitution ratio based on the maximum stability and equivalent air voids is about 1.7 1. Since minimizing the substitution ratio has a direct impact on the economic benefits to be realized by replacing the asphalt with sulfur these justification tests are to be recommended in all mix designs. 

Figure 15, Sulfur-extended asphalt (SEA) justification test data. Curve 1, asphalt binder and Curve 2, SEA binder (30-70) (33).

Furthermore, a method for determining the colorfastness of pigments in binders in the presence of sulfur dioxide is also prescribed. The test is carried out simultaneously on ten identical samples and consists of three cycles. Apparatus condensation equipment. 

Rheology of SA Binders. Conventional test methods such as softening point, viscosity, penetration, Fraas break point, ductilities, etc. have been used to characterize the rheology of SA binders (11). The physical structure of SA binders is complex, and the sulfur-asphalt and sulfur-aggregate interaction make correlations to asphalt and to binder properties for aggregate rather difficult. 

Sulfui>-Aggregate Interaction. Substantial increases in stiffness of SA binder-based mixes, as measured by the Marshall test, tensile strength, and resilient modulus of elasticity, have been observed with increasing sulfur-asphalt ratio of the binder used (11, 15, 16). Such increases can, of course, be attributed in part to the increase in viscosity of the SA... 

The SA binder is tested for dispersion and particle size prior to mix production with a microscope. The binder level of the mix is constantly measured with a Troxler model 2226 asphalt content gauge. Hot solvent extraction (ASTM D2172) using tetrachloroethylene solvent can also be used to measure the binder content of a SA mix. The sulfur—asphalt ratio of the binder is monitored in the field with the Troxler or by density measurements. Other methods that can be used to measure SA ratios are x-ray fluorescence of solutions of sulfur-asphalt in tetrachloroethylene, liquid chromatography, and differential scanning calorimetry. X-ray fluorescence measures total sulfur, liquid chromatography determines elemental sulfur, and DSC monitors crystalline sulfur. 

A test program to determine the feasibility of direct substitution of sulfur for asphalt in preparing sulfur-asphalt concretes was conducted. Properties of the resultant materials were compared with those of emulsified sulfur-asphalt binder materials and conventional materials. In addition, a test program was conducted to determine if direct-substituted binders could be used to upgrade marginal aggregates for use in paving materials. 

Evaluation of sulfur-asphalt binders for paving materials showed no differences in materials prepared using either the emulsified or the direct substitution method in preparing the binder. Therefore, the simpler direct substitution method was used in all subsequent testing. 

Temperature sensitivity tests were made on these materials, and the results are shown in Figures 12 and 13. From the results it is. evident that substitution of 35-vol % sulfur in the binder improves the stability of the sand paving with the same level of voids and flow. The material is workable down to a 190°F compaction temperature. Larger amounts... 

Figure 2. The optimum asphalt binder concentration was 4.5 wt %, and this volume of binder was used in all tests. Properties of the paving materials prepared from the limestone with asphalt and with sulfur-asphalt binders are shown in Table VI.

Marshall stability of asphalt concrete dropped 72% after immersion testing in gasoline compared with only a 21% loss with 35-vol % sulfur-asphalt concrete. Jet and diesel fuels had a lesser effect on the Marshall stabilities than did gasoline. The solvent effect on sulfur-asphalt concrete materials decreased with increasing sulfur content in the asphaltic binder in the O-35-vol % substitution range. The greater resistance of sulfur-... 

Test Strips. Larger batches of direct-substituted sulfur-asphalt paving mixtures were prepared with type IVb aggregate materials. Mixtures containing 0-, 15-, 25-, and 35-vol % sulfur in the asphalt binder were... 

Highway District 11 is located in East Texas, and the area does not have an abundant supply of conventional aggregates. Of the materials available locally, sand is the most plentiful. These local sands were first combined with asphalt in a hot-mix plant in 1962 and were evaluated on U.S. and State highways. From this experience, it was concluded that hot-hand asphalts merited consideration as base materials. Quite often two sands (usually 100% passing the 40 sieve) are combined to obtain the proper gradation. When it was subsequently learned that the Texas Transportation Institute (13) was evaluating the sulfur-asphalt binders, efforts were initiated to field test these materials. 

This report will describe the design, construction, and performance of a test highway in which a sulfur-asphalt binder was used with sand alone and sand-gravel aggregates. The program was quite comprehensive and included the study of other variables such as thickness and amount of binder. 

Figure 1. Layout of SNPA sulfur-asphalt binder pavement test, US highway...

The design of the test sections is illustrated in Figure 1. Binders were selected which contained 30% sulfur by weight. As high a substitution ratio as possible was desired to minimize asphalt usage, and, at the time,... 

The allowable sulfur concentration in the binder depends on the properties of the asphalt. For example, asphalts A and B (Appendix, Table A-I) exhibit significantly different viscosities at the Marshall test temperature of 60°C. This difference is reflected by differences in mix stability at similar asphalt contents, shown in the Appendix and in Figure 6, i.e., 11120 N and 5960 N for asphalt A and B, respectively, at a content of 6 wt %. Asphalt B yields high-stability mixes and is not as prone to softening by low sulfur concentrations in the binder, whereas asphalt A exhibits the reverse behavior. 

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